This invention relates generally to methods and apparatus for attaching soft tissue to bone, and more particularly to anchors and methods for securing connective tissue, such as ligaments or tendons, to bone. The invention has particular application to arthroscopic surgical techniques for reattaching the rotator cuff to the humeral head, in order to repair the rotator cuff.
It is an increasingly common problem for tendons and other soft, connective tissues to tear or to detach from associated bone. One such type of tear or detachment is a “rotator cuff” tear, wherein the supraspinatus tendon separates from the humerus, causing pain and loss of ability to elevate and externally rotate the arm. Complete separation can occur if the shoulder is subjected to gross trauma, but typically, the tear begins as a small lesion, especially in older patients.
To repair a torn rotator cuff, the typical course today is to do so surgically, through a large incision. This approach is presently taken in almost 99% of rotator cuff repair cases. Two types of open surgical approaches for repair of the rotator cuff, one known as the “classic open” and the other as the “mini-open”. The classic open approach requires a large incision and complete detachment of the deltoid muscle from the acromion to facilitate exposure. Following the suturing of the rotator cuff to the humeral head, the detached deltoid is surgically reattached. Because of this maneuver, the deltoid requires postoperative protection, thus retarding rehabilitation and possibly resulting in residual weakness. Complete rehabilitation takes approximately 9 to 12 months.
The mini-open technique, which represents the current growing trend and the majority of all surgical repair procedures, differs from the classic approach by gaining access through a smaller incision and splitting rather than detaching the deltoid. Additionally, this procedure is typically used in conjunction with arthroscopic acromial decompression. Once the deltoid is split, it is retracted to expose the rotator cuff tear. The cuff is debrided to ensure suture attachment to viable tissue and to create a reasonable edge approximation. In addition, the humeral head is abraded or notched at the proposed soft tissue to bone reattachment point, as healing is enhanced on a raw bone surface. A series of small diameter holes, referred to as “transosseous tunnels”, are “punched” through the bone laterally from the abraded or notched surface to a point on the outside surface of the greater tuberosity, commonly a distance of 2 to 3 cm. Finally, the cuff is sutured and secured to the bone by pulling the suture ends through the transosseous tunnels and tying them together using the bone between two successive tunnels as a bridge, after which the deltoid muscle must be surgically reattached to the acromion.
Although the above described surgical technique is the current standard of care for rotator cuff repair, it is associated with a great deal of patient discomfort and a lengthy recovery time, ranging from at least four months to one year or more. It is the above described manipulation of the deltoid muscle together with the large skin incision that causes the majority of patient discomfort and an increased recovery time.
Less invasive arthroscopic techniques are beginning to be developed in an effort to address the shortcomings of open surgical repair. Working through small trocar portals that minimize disruption of the deltoid muscle, a few surgeons have been able to reattach the rotator cuff using various bone anchor and suture configurations. The rotator cuff is sutured intracorporeally and an anchor is driven into bone at a location appropriate for repair. Rather than thread the suture through transosseous tunnels which are difficult or impossible to create arthroscopically using current techniques, the repair is completed by tying the cuff down against bone using the anchor and suture. Early results of less invasive techniques are encouraging, with a substantial reduction in both patient recovery time and discomfort.
Unfortunately, the skill level required to facilitate an entirely arthroscopic repair of the rotator cuff is inordinately high. Intracorporeal suturing is clumsy and time consuming, and only the simplest stitch patterns can be utilized. Extracorporeal knot tying is less difficult, but their tightness cannot later be adjusted. Knots tied arthroscopically are difficult to achieve, impossible to adjust, and are located in less than optimal areas of the shoulder. Suture tension is also impossible to measure and adjust once the knot has been tied. Consequently, because of the technical difficulty of the procedure, presently less than 1% of all rotator cuff procedures are of the arthroscopic type, and are considered investigational in nature.
A significant difficulty with current arthroscopic rotator cuff repair techniques are shortcomings related to currently available suture anchors. Suture eyelets in bone anchors available today are small in radius, and can cause the suture to fail at that location when the anchor is placed under high tensile loads. Additionally, the sutures must be preloaded into the anchor. Thus, if the suture breaks or is accidentally pulled out during manipulation, a new anchor must be used. The old anchor remains in the bone, because of a barbed construction designed to resist axial removal of the anchor. This presents a problem because of the limited bone space available for the insertion of bone anchors. The need to utilize additional bone anchors to satisfactorily complete a procedure, leaving extra useless anchors in the bone, can severely compromise the ability to perform subsequent procedures, should they be required. Furthermore, due to design, some anchors are limited in the way that they can be placed into the bone. For example, two Mitek anchors must not be placed too near one another or too near the edge of a bone as the “retention barbs” present on anchors of this particular design would interfere with each other or fall outside the surface of the bone. A major problem with existing suture anchor designs is the location of the suture attachment point (typically an eyelet) at the exposed proximal end of the anchor. This arrangement means that any tensile force applied on the suturing material attached to the anchor will result in an axial pull-out force applied to the anchor. As a consequence, if the suturing material itself does not break at the point of attachment, as discussed supra, then there is still a substantial risk that the bone anchor will pull out of the bone, causing the connective tissue to once again become at least partially detached from the bone. In the humerus, the cancellous bone is soft, making such an event more likely. If either suture failure or anchor pull-out occurs after the surgical procedure has been completed, then an entirely new repair procedure must be initiated, with its attendant costs, discomfort, inconvenience, and rehabilitation.
Other methods of securing soft tissue to bone are known in the prior art, such as staples and tacks, but are not presently considered to be feasible for shoulder repair procedures, because of physicians' reluctance to leave anything but a suture in the capsule area of the shoulder. The reason for this is that staples, tacks, and the like could possibly fall out and cause injury during movement. Screws are also known for such attachment procedures, but suffer from a number of disadvantages, including their tendency to loosen over time, requiring a second procedure to later remove them, and their requirement for a relatively flat attachment geometry. As a result of this constraint, the attachment point often must be located at a less than ideal position.
What is needed, therefore, is a new approach for repairing the rotator cuff, wherein suture tension can be measured and adjusted, the suture resides completely below the cortical bone surface, there is no requirement for the surgeon to tie a knot to attach the suture to the bone anchor, and the skill level for correct placement is suitable for practitioners having average ability.